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  1. #1
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    How hard for someone with no framebuilding experience to construct a Brompton fork?

    I like folding bikes, however there are aspects of their design that persistently frustrate me. I find myself wanting to redesign them myself.

    I've never brazed anything, never sourced lugs, crowns etc.. How tricky would it be and what cost would be involved would in attempting to replicate something like this?:



    The geometry is unique: how would I obtain fork blades of the correct length? Would it be easy to find a crown of that flat shape so that the threaded section could be brazed on top (with 1 1/8 steerer)? What problems will likely arise?

    The primary reason for doing this would be to have a threadless steerer tube, and then to redesign part of the stem, it's an idea that's been floating round my head for a while now and I figure I ought to get a better idea of the feasibility.

  2. #2
    Senior Member mudboy's Avatar
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    Wouldn't be difficult for someone who's done it before, but not a job for an absolute novice.

    However, if all you want to do is replace the steerer, that's more do-able, as the steerer tube is about the easiest piece to braze. Getting it hot enough to remove is another story. And, of course, you'd need to strip the paint off the fork first.
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  3. #3
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    A suggestion , take a look at a" Dursley Pedrerson" design using small dia. tubes , A head set . ,alloy disc brake

  4. #4
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    Steering tubes, off of a suspension fork ,Bottom and top fixing by current star washer systems, Make your own do a "Instructables"

  5. #5
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    Quote Originally Posted by mudboy View Post
    Wouldn't be difficult for someone who's done it before, but not a job for an absolute novice.

    However, if all you want to do is replace the steerer, that's more do-able, as the steerer tube is about the easiest piece to braze. Getting it hot enough to remove is another story. And, of course, you'd need to strip the paint off the fork first.
    Is swapping out a steerer a not atypical procedure then? I did a quick search on this recently and I thought I detected a rough consensus that it would weaken the fork too much to be safe? Getting a slightly longer threadless steerer is the primary objective, though I'm also interested in learning about frame construction in general.
    Last edited by chagzuki; 02-11-12 at 04:18 PM.

  6. #6
    Randomhead
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    most framebuilders will not touch a steerer replacement. There are a few that will splice a new steerer onto the old one. Rody at Groovy has a video somewhere of how he does it, a quick search failed to find it

  7. #7
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    If I were to make it from scratch what'd be the best solution for the fork blades? I don't know how it's normally done. . . I'm imagining that in this case I'd source some standard size blades and cut them down. But perhaps this wouldn't make for a clean fit in the crown? The other consideration is that the front hub is 74mm OLD.

  8. #8
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    I've got a pair of True Temper recumbent fork blades that I'm not particularly attached to, but depending on the length needed I'd probably just look into cutting down regular blades as necessary. Ride is clearly not something that is a big concern judging from the fork in the photo.

    I've also cut down a bonded alumnium straight leg mtb fork in the past, if the rake is what you want it isn't that huge a deal, but that doesnt the 74 old issue.

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